While some of the benefits — like a lift in mood — can emerge as soon as a few minutes into a sweaty bike ride, others — like improved memory — might take several weeks to crop up. That means that the best type of fitness for your mind is any aerobic exercise that you can do regularly and consistently for at least 45 minutes at a time.

In the latest study to assess the benefits of aerobic workouts on the brain, researchers looked to hundreds of breast cancer survivors. They wanted to see if activities like walking and swimming could have any effect on "chemo brain," a commonly-reported side effect of breast cancer treatment that involves memory loss and difficulties focusing.

Since previous research had suggested that regular workouts could help protect against age-related cognitive decline, the researchers wanted to find out if those results would hold true for cancer survivors too.

They gave nearly 300 breast cancer survivors accelerometers to track their daily activity and access to a specially-designed iPad app called BrainBaseline outfitted with quizzes designed to measure their attention and memory. At the end of a week, people who'd done aerobic exercise every day were not only significantly less tired than those who did little to no exercise, but also did significantly better on the app's quizzes.

"The message for cancer patients and survivors is, get active!" said Diane Ehlers, the lead author on the study and a professor of exercise psychology at the University of Illinois at Urbana Champaign, in a statement.

Given that the study was only a week long, more research on cancer patients in particular is needed. Still, the evidence that aerobic workouts have a wide range of potential beneficial impacts on the brain — from reducing the symptoms of depression to strengthening connections in parts of the brain linked with memory — is robust and growing.

A pilot study in people with severe depression found that just 30 minutes of treadmill walking for 10 consecutive days was "sufficient to produce a clinically relevant and statistically significant reduction in depression." Aerobic workouts can also help people who aren't suffering from clinical depression feel less stressed by helping to reduce levels of the body's natural stress hormones, such as adrenaline and cortisol, according to a recent study in the Journal of Physical Therapy Science.

If you're over 50, a study in the British Medical Journal suggests the best results come from combining aerobic and resistance exercise, which could include anything from high-intensity interval training, like the 7-minute workout, to dynamic flow yoga, which intersperses strength-building poses like planks and push-ups with heart-pumping dance-like moves. Another study published in May provides some additional support to that research, finding that in adults aged 60-88, walking for 30 minutes four days a week for 12 weeks appeared to strengthen connectivity in a region of the brain where weakened connections have been linked with memory loss.

Researchers still aren't sure why this type of exercise appears to provide a boost to the brain, but studies suggest it has to do with increased blood flow, which provides our minds with fresh energy and oxygen. And one recent study in older women who displayed potential symptoms of dementia found that aerobic exercise was linked with an increase in the size of the hippocampus, a brain area involved in learning and memory.

Joe Northey, the lead author of the British study and an exercise scientist at the University of Canberra, said his research suggests that anyone in good health over age 50 should do 45 minutes to an hour of aerobic exercise "on as many days of the week as feasible."